textproduct: Rapid City

KEY MESSAGES

- Isolated to scattered showers/storms increase from southwest to northeast in the overnight hours.

- Slight risk of severe thunderstorms Thursday afternoon/evening, mainly across northeastern WY

- Active pattern continues with chances for severe storms Friday and Saturday, though there is still some uncertainty in location and timing.

UPDATE

Issued at 927 PM MDT Wed Jun 24 2026

Forecast remains mostly on track for the near term. Some minor tweaks to QPF and PoPs in the overnight hours. Showers increase in coverage overnight into Thursday morning. Main concern for Thursday continues to be severe storm potential. Low level southeast flow may allow cloud coverage to maintain into much of Thursday, limiting the energy storms would be able to tap into. HRRR tend to be more aggressive on severe activity, but will have to see if/how cloud cover inhibits development.

DISCUSSION

(This Afternoon Through Tuesday) Issued at 1149 AM MDT Wed Jun 24 2026

Upper air analysis depicts weak wave moving across northeastern WY into western SD. The disturbance has triggered the development of a few showers/storms over northeastern WY and the Black Hills. This activity should continue through the afternoon and evening hours as 500 mb speed max remains over the region. Bulk shear values of 40-50kt and modest instability of 500-1000 J/kg should contribute to a marginal severe threat across portions of northeastern WY into southwestern SD with the main hazards being large hail and damaging winds.

Near zonal flow pattern continues through Thursday with another shortwave moving across the Northern Plains by the afternoon/evening hours. Morning cloud cover may limit daytime heating and overall severe potential with 12z models showing ~500-1500 J/kg CAPE over the far western reaches of our CWA by 3 pm tomorrow afternoon. Most recent CAMs indicate a line of storms developing off the Big Horns tomorrow afternoon with initial storm development having the greatest severe potential (main hazards will be large hail and damaging winds). The line of storms will move eastward through the CWA as the evening progresses. While a few storms may become strong and we could see some severe caliber wind gusts as the line moves through, as of now not anticipating any widespread severe weather across western SD as the storms move through.

Longwave trough moves into the western US on Friday with zonal westerly flow over our neck of the woods transitioning to southwest flow. Southeasterly sfc flow will bring warm, moist air into the region with ML CAPE values rising to 2000 to 3000 J/kg across western SD by the late afternoon/evening hours. However weak upper level ridging and warm 750 mb temps contributing to a strong cap will likely keep the severe threat conditional for Friday.

Attention turns to severe potential on Saturday as a shortwave and attendant lee cyclone moves through the region. There's still some uncertainty as to the timing and location of the lee cyclone and where the greatest instability will be by the afternoon. So correspondingly, confidence is low in the exact location and timing of any severe weather risks for Saturday with the most likely area to see severe weather across portions of northwestern and north central SD.

AVIATION

(For the 00Z TAFS Through 00Z Thursday Evening) Issued At 521 PM MDT Wed Jun 24 2026

Low VFR (040-100) cigs are expected for much of the TAF period for the southern half of our forecast area. The TAF sites are not expected to go below VFR. Far southwestern SD into the southern Black Hills could see MVFR/IFR cigs Thursday morning into the afternoon. Showers/storms are ongoing east of the Black Hills into south central SD and will continue to move east this evening. More shower/storms move in tonight into Thursday morning, affecting mainly southwestern SD and northeast Wyoming. Low confidence that they will affect the TAF sites.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.